In the fictitious scenario, observers continued to track the asteroid for three months using ground-based telescope observations, and the probability of impact climbed to 65 percent. Then the next observations had to wait until four months later, due to the asteroid's position relative to the sun.

Once observations could resume in May of 2017, the impact probability jumped to 100 percent. By November of 2017, it was simulated that the predicted impact would occur somewhere in a narrow band across Southern California or just off the coast in the Pacific Ocean.

The THIRD in a series of exercises hosted jointly by NASA and FEMA -- the Federal Emergency Management Agency -- the simulation was designed to strengthen the collaboration between the two agencies, which have Administration direction to lead the U.S. response.

"It's not a matter of if -- but when -- we will deal with such a situation," said Thomas Zurbuchen, Associate Administrator for NASA's Science Mission Directorate in Washington. "But unlike any other time in our history, we now have the ability to respond to an impact threat through continued observations, predictions, response planning and mitigation."

THE TEA ROOM HAS OFFERED SEVERAL ARTICLES, SOME RECENTLY SUCH AS <THIS> AND <THIS>, TO TRY TO CALL ATTENTION TO THE "TREND" OF NASA AND OTHER AGENCIES IN SEEKING A "NEW EARTH", OF BEING IN A HURRY TO COLONIZE THE MOON, MARS, 'OTHER WORLDS', OF THE MILITARY AND THE FEDERAL RESERVE, ETC, MOVING FACILITIES BACK DEEP UNDERGROUND OVER THE PAST FEW YEARS, AND THE 'DISCOVERIES' THAT WE'RE BEING HIT MORE OFTEN THAT PREVIOUSLY THOUGHT BY SPACE OBJECTS, THAT OUR IONOSPHERE WAS PEELED AWAY JUST A BIT BY A "COSMIC EVENT" IN 2005, AND THE PRESIDENT ADDRESSING THESE ISSUES IN AN EXECUTIVE ORDER LAST MONTH....

The goal is to learn how to better deflect comets and asteroids that might endanger cities and, in the case of very large intruders, the planet as a whole.

In interviews, federal officials and private experts said the new interagency agreement would deepen the levels of expert cooperation and governmental planning, ultimately increasing the chances of a successful deflection.

“It’s a big step forward,” said Kevin Greenaugh, a senior official at the nuclear security agency. “Whenever you have multiple agencies coming together for the common defense, that’s news.”

The agency also released a computer app that — at least in theory — lets amateur astronomers help the agency find new asteroids.

WELL, THAT'S GREAT, BUT THOSE GUYS WANT TO USE NUCLEAR WEAPONS TO DEFLECT SPACE OBJECTS. WHAT'S UP WITH ALL THAT?

An example of prior federal research comes from the Los Alamos weapons lab in New Mexico, the birthplace of the bomb.

AND WHAT COULD POSSIBLY GO WRONG WITH LOS ALAMOS AND LAWRENCE LIVERMORE LAB INVOLVED, RIGHT?

An astrophysicist there, Robert Weaver, ran supercomputer simulations that the lab hailed in an article two years ago as exploratory steps for “Killing Killer Asteroids.” It quoted him as saying such research “will hopefully give policy makers a better understanding of what their options are.”

And eight years ago, NASA scientists detailed plans for an interceptor rocket tipped with a B83 — a warhead about 75 times as powerful as the Hiroshima bomb.In interviews, officials have declined to say whether any specific arms in the nation’s nuclear arsenal have been set aside for countering extraterrestrial strikes.

“There’s a discussion,” David S.P. Dearborn, an astrophysicist at the Lawrence Livermore National Laboratory in California, said in an interview, “about what should be held onto” even as the country seeks to modernize and trim its nuclear stockpile in accordance with disarmament treaties"

The simulation that projected a strike in 2020 involved representatives from NASA’s Jet Propulsion Laboratory, the Department of Energy’s National Laboratories, the Air Force and the California Governor’s Office of Emergency Services.

While a warning of four years may seem like a lot of time, it would probably not be enough to deflect an asteroid of the size and orbit outlined in the simulation, Paul Chodas of NASA said.

DON'T WORRY, BE HAPPY. An asteroid that could cause such damage has no significant chance of striking Earth within the next century, Chodas, manager of NASA’s Center for Near-Earth Object Studies at the Jet Propulsion Laboratory in Pasadena, Calif., said in an email.

EX-ASTRONAUTS AND OTHERS IN THE SCIENTIFIC COMMUNITY DISAGREE.Asteroid Day, a global movement that seeks to protect the world from dangerous asteroids, maintains that one million asteroids have the potential to strike Earth but that only 1 percent of them have been discovered

The group promotes the “100x Declaration,” which calls for increasing the rate of asteroid discoveries to 100,000 per year in the next 10 years.

“The more we learn about asteroid impacts, the clearer it became that the human race has been living on borrowed time,” Brian May, an astrophysicist and a founder and lead guitarist for the rock group Queen, said on the group’s website. [YES, HE REALLY IS AN ASTROPHYSICIST.]

In a squabble over data from the Wide-field Infrared Survey Explorer spacecraft (WISE), launched in 2009, NASA snapped images of three-quarters of a billion stars, galaxies and other celestial objects, including the heat emissions of asteroids.

An offshoot called Neowise used the heat data to calculate the size and reflectivity of 158,000 asteroids.

Dr. Nathan P. Myhrvold, once the chief technologist at Microsoft, contends that the Neowise analysis is deeply flawed. “The bad news is it’s all basically wrong,” he said. “Unfortunately for a lot of it, it’s never going to be as accurate as they had hoped.”

Dr. Myhrvold concluded that the ground-based telescope in Chile, a $665 million collaboration of the United States Department of Energy, the National Science Foundation and other organizations, could find up to 90 percent of near-Earth asteroids if it spent more time looking low in the sky, closer to the Earth’s horizon.

NEOWISE DATA IRREPRODUCIBLE...

Dr. Myhrvold insists he has no vendetta against the Neowise scientists. But, he added, “I don’t think it’s unduly mean of me to point out their data is irreproducible.”

Most of the millions of asteroids are found between the orbits of Mars and Jupiter, but some dip closer to the sun. There is no doubt that some will hit Earth someday.

The largest space-related explosion in human history, an asteroid strike in Tunguska, Siberia, in 1908, may have been caused by an asteroid, believed to be less than 100 feet in diameter. It exploded at the altitude of an airliner and flattened tens of millions of trees across 800 square miles. Researchers estimated the explosion was as powerful as a medium-size hydrogen bomb and several hundred times more powerful than the atomic bomb dropped on Hiroshima.

While there were no official reports of human casualties, hundreds of reindeer were reduced to charred carcasses in the explosion, the British Broadcasting Corporation reported.

Scientists have suggested that the Earth is vulnerable to many more Chelyabinsk-size space rocks. In research published in 2013 by the journal Nature, they estimated that such strikes could occur as often as every decade or two instead of an average of once every 100 to 200 years as previously thought." AND THEN THERE ARE THE "UNEXPECTED, UNFORESEEN SOLAR EVENTS" LIKE...